mex: windows_shortname()

Author: scivision

+stdlib/windows_shortname.m

@@ -11,7 +11,7 @@
   p (1,1) string
 end
 
-s = string.empty;
+s = "";
 
 if ~ispc || stdlib.is_url(p)
   return

private/get_mex_sources.m

@@ -10,6 +10,13 @@
   fullfile(top, "src/set_permissions.cpp"), ...
 };
 
+s = fullfile(top, "src/windows_shortname.cpp");
+if ispc
+  s(end+1) = fullfile(top, "src/windows.cpp");
+end
+srcs{end+1} = s;
+
+
 % isSymbolicLink() new in R2024b
 if ~isMATLABReleaseOlderThan("R2024b")
 

src/win32_fs.h

@@ -1 +1,5 @@
-bool fs_win32_is_symlink(std::string path);
+#include <string>
+
+bool fs_win32_is_symlink(std::string);
+
+std::string fs_shortname(std::string);

src/windows.cpp

@@ -1,5 +1,6 @@
 #include <string>
 #include <cstddef>
+#include <cstdlib> // for _MAX_PATH
 
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
@@ -118,3 +119,20 @@ bool fs_win32_is_symlink(std::string path)
          (reparseTag == IO_REPARSE_TAG_MOUNT_POINT);
 
 }
+
+
+std::string fs_shortname(std::string in)
+{
+// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getshortpathnamew
+// the path must exist
+
+  std::string out(_MAX_PATH, '\0');
+// size does not include null terminator
+  if(auto L = GetShortPathNameA(in.data(), out.data(), static_cast<DWORD>(out.size()));
+      L > 0 && L < out.length()){
+    out.resize(L);
+    return out;
+  }
+
+  return {};
+}

src/windows_shortname.cpp

@@ -0,0 +1,55 @@
+// C++ Matlab MEX function using C++17 <filesystem>
+// https://www.mathworks.com/help/matlab/matlab_external/data-types-for-passing-mex-function-data-1.html
+
+#include "mex.hpp"
+#include "mexAdapter.hpp"
+
+#include <string>
+// note: <string_view> causes compile failures with MSVC at least
+
+#include <vector>
+#include <memory>
+
+#if defined(_WIN32)
+#include "win32_fs.h"
+#endif
+
+
+class MexFunction : public matlab::mex::Function {
+public:
+  void operator()(matlab::mex::ArgumentList outputs, matlab::mex::ArgumentList inputs) {
+// boilerplate engine & ArrayFactory setup
+    std::shared_ptr<matlab::engine::MATLABEngine> matlabPtr = getEngine();
+
+    matlab::data::ArrayFactory factory;
+// boilerplate input checks
+    if (inputs.size() != 1) {
+      matlabPtr->feval(u"error", 0,
+        std::vector<matlab::data::Array>({ factory.createScalar("One input required") }));
+    }
+    if (inputs[0].getType() != matlab::data::ArrayType::MATLAB_STRING) {
+      matlabPtr->feval(u"error", 0,
+        std::vector<matlab::data::Array>({ factory.createScalar("Input must be a string") }));
+    }
+    if (inputs[0].getNumberOfElements() != 1) {
+      matlabPtr->feval(u"error", 0,
+        std::vector<matlab::data::Array>({ factory.createScalar("Input must be a scalar string") }));
+    }
+
+// Matlab strings are an array, so we use [0][0] to get the first element
+    std::string inputStr = inputs[0][0];
+
+// actual function algorithm / computation
+#if defined(_WIN32)
+    std::string s = fs_shortname(inputStr);
+#else
+    std::string s = "";
+#endif
+
+// convert to Matlab output -- even scalars are arrays in Matlab
+// https://www.mathworks.com/help/matlab/matlab_external/create-matlab-array-with-matlab-data-cpp-api.html
+// https://www.mathworks.com/help/matlab/apiref/matlab.data.arrayfactory.html
+
+    outputs[0] = factory.createScalar(s);
+  }
+};

test/TestWindowsCOM.m

@@ -7,7 +7,7 @@
 methods (Test)
 
 function test_not(tc, Pn)
-tc.verifyEmpty(stdlib.windows_shortname(Pn))
+tc.verifyEqual(stdlib.windows_shortname(Pn), "")
 end
 
 function test_short_folder(tc)